This invention relates to gas-filled proportional counters and more particularly to a construction which eliminates end effects.
In general, conventional proportional counters comprise two electrodes in a surrounding of a desired gas at a desired pressure. Radiation entering the proportional counter ionizes the gas molecules therein to produce ions. The negatively charged ions produced will travel to the anode whereas the positively charged ions travel in the opposite direction to the cathode. The resulting output of the counter is a measure of the energy of the ionizing radiation which enters into the ionization chamber.
It is well known in the art that proportional counters produce electrical pulses in response to the absorption of a photon. When photons are absorbed near the ends of gas-filled proportional counters, the pulse amplitudes produced are less than if absorption had taken place in the middle of the counter. Conventionally, the ends of the proportional counter are not used, i.e., masks are placed so that no photon absorption occurs near the ends. Therefore a potentially useful part of the prior art counters are not being utilized. This may be a serious disadvantage whenever weight and volume are important.